Should I focus on SMB sales for getting my first few ICPs and then building the product?

I am building a B2B product for engineering teams and trying to decide whether to start with SMBs or pursue larger companies from day one.

Larger organizations may have stronger budgets, but they often already use internal tools and have longer sales cycles. Smaller companies seem easier to reach and more likely to feel the problem, but I’m concerned that optimizing for early SMB customers could pull the product away from the enterprise market.

Would you use SMB sales mainly for customer discovery and early traction, then move upmarket, or define the long-term ICP before building further?